<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<style>
#one{
 color:red;
 font-size:24px;
}
#two{
 color:blue;
 font-size:36px;
}
#three{
 color:green;
 font-size:48px;
}
</style>
<title>Insert title here</title>
</head>
<body>
<p id="one">ID选择器1</p>
<p id="two">ID选择器2</p>
<p id="three">ID选择器3</p>
</body>
</html>